This type of hydraulic shock absorber is disclosed in JP 11-72133 A.
This hydraulic shock absorber can variably control damping forces generated in an extension stroke and a compression stroke independently of each other.
In this case, while a spool for generating a damping force is urged through pilot pressure set by a poppet valve in the extension stroke, the spool is directly urged by a spring in the compression stroke. A magnetic force of a solenoid is applied in such a direction as to reduce an urging force of the spring, so the damping force can be variably controlled based on current through the solenoid.